how do I change environments in ruby on rails

At the moment, I am unable to run my server because apparently I seem to be in the wrong environment.

Suppose I am in the test environment, how do I switch to the production environment? Because right now, every time I am trying to run my app they keep telling me the server is running on the production environment.When I check to see if its running it still says that no application is running....

Is there a command I can use to switch environments?